I know this is an old thread but...I have the same mower with the same problem...i have removed and cleaned the tank vent, replaced the fuel pump, fuel filter and gas cap with new from JD. Problem is getting worse...Last year it only did this when blades were not engaged. When blades were engaged or mower was under a load (pulling a garden trailer) it ran fine. This year it does it all the time. As the engine RPM's drop on the surge while cutting I all but have to stop and allow the engine to come back up to speed to continue...Ant Ideas will be welcomed.